High-erequency multiplex signaling system



July 29 1924.

LM-EEH=EPJSCZFHEZD HIGH FREQUENCY MULTIPLEX SIGNALING SYSTEM OriginalFiled Sent. 30. 1919 I wi smto z llflf/velzsciad Patented July 29,1924..

UNITED STATES PATENT OFFICE.

LLOYD ESPENSCHIED, 033 QUEENS, NEW YORK, ASSIGNOR T0 AMERICAN TELEPHONEAND TELEGRAPH COMPANY, A. COREGRATION OF NEW YORK.

HIGH-FREQUENCY IMULTIPLEX SIGNALING SYSTEM.

Original application filed September 30, 1919, Serial No. 327,500.Divided and. this application filed April Te ((15 107mm it may concern:

Be it known that I, LLOYD ESPENSGHIED, residing at Queens, in the countyof Queens and State of New York, have invented certain improvements infliglrFrequency Multiplex Signaling Systems, of which the following is aspecification.

T his invention. relates to high frequency multiplex signaling systemand more particularly to a terminal circuit arrangement embodying theuse of a common translating circuit adapted both to modulate the transmitted current and to demodulate the high frequency received current.

This application is a division of my copending application Serial No.327 500 filed September 30, 1919, entitled high frequency multiplexsignaling systems.

In the multiplex signaling systems heretofore used which employ aplurality of carrier currents of various frequencies, it has beencustomary to insert in the transmittting and the receiving branches ofthe terminal circuit a translating device individual to each of saidbranches. It is the object of the present invention to adaptthe'terminal circuit arrangement so that the processes of modulation,demodulation and amplification of the various currents in both thetransmitting and receiving branches of the terminal circuit may beperformed by a single translating device. Although the preferable formof translating device is a single thermionicvacuum tube or a pluralityof such tubes in combination adapted to function as a single unit withrespect to the two branches of the terminal circuit, yet any well knowntype of translating device such as the mechanical repeater may be used.

Another object of this invention is to provide a circuit arrangementofthe general character described above in which the filters are insertedin the two-wire circuits, that is to say between the line circuits andthe triple winding transformer which serves to connect the commontranslating circuit with the twowire vsignaling circuits.

Other and further objects of this invention will be apparent from'thefollowing description when read in connection with the attached drawingof which Figure 1' shows an arrangement employing two triple windingtransformers in which the third Serial No. 461,966.

winding of each transformer is connected in parallel with the outputcircuit of the translating circuit; and Figure 2 shows an arrangement inwhich a single triple winding transformer is used which is arranged forthe transformation of both the high frequency and the low frequencycurrents.

Figure l v shows a variation of the type of circuit described in mycopending application referred to hereinbefore, in which a singletranslating unit performs both functions of modulation and demodulationfor the two sides of'the circuit, the variation consisting in theplacing of the high frequenc} and the low frequency filters in thetwo-wire portions as distinguished from the four-wire portion ofthecircuit. The circuit arrangement shown in the upper part of this figurerepresents one of the terminal circuits for the reception ortransmission of one of the bands of frequencies based upon a definitecarrier frequency, which may be transmitted or received over the maintransmission circuit ML. In the circuit arrangement L, represents a lowfrequency signaling circuit. which is connected with the windings of thetriple winding transformer T and is balanced by the network N Interposedbetween the line L, and the said transformer, and the network and thesaid transformer. are low frequency band filters F and F The highfrequency line L is connected with the windings of another triplewinding transforn'ier T with which is connected a balancing network Nadapted to balance the high frequency line. Interposed between the lineand the said transformer, and'the network N, and the said transformer,are the high frequency band filters E, and, ll, respectively. Themidpoints of two of the windings of each transformer, T and T connectedwith linesL and L are connected in parallel, the, said connectionembracing one of the windings of the transformer T The third windings ofthe transformers T and T are connected in parallel, the said connectionembracing one of the windings of the output transformer T of thetranslating circuit. Inductances C and C are inserted in the conductorsconnecting the said third windings of transformers T and T with theoutput transformer T, in order to prevent the passage of high frequencyoscillations between the transformer T and T In the operation of thiscircuit low fre quency voice currents from line L will pass through thelow frequency band filter F and will be impressed across the midpointsof the windings of the coil T with which the line L is connected. Thesesignaling currents will in. turn be impressed by the coil 1 of the inputtransformer T upon the coil 2 of the said transformer, and willacordingly modulate the high frequency oscillations which are impressedupon the translating circuit by the source 3. The modulated highfrequency oscillations will pass through the output transformer T andwill be 1mpressed by the windingl of the transformer T upon the highfrequency circuit L The high frequency currents are excluded from thelow frequency circuit by inductances C and-C and filters F F The highfrequency modulated waves will pass through the high frequency bandfilter F to the main transmission line ML, and thence to the terminalcircuit at the opposite end of the said line. The modulated highfrequency oscillations received over the transmission line ML will beconducted by the circuit L through band filter F to the midpoint of thewindings of transformer T These oscillations will be impressed acrosswinding 1 of transformer T and will pass through the translating deviceand be demodulated thereby. The low frequency demodulated current willpass through inductances C and G which offer substantially no impedanceto low frequencies, to the winding 6 of transformer T and will impressedupon the low frequency line L passing through the band filter F The lowfre quency currents are excluded from the high frequency circuit bycondenser 5 and the high pass filters F F This circuit arrangementillustrates a method by which the high frequency and the low frequencycurrents may be impressed upon a common translating device by means ofbalancing coils which are connected effectively in parallel. It. shouldbe understood that any number of terminal circuits similar to the onedescribed may be connected with the main transmission line, the terminalcircuits being made selective by the inscrtion in each branch highfrequency circuit of a band lilter similar to F but adapted to transmitany desired band of frequencies for the specific terminal circuit.Further more, a low frequency signaling circuit L might be connectedwith the transmission line through a suitable low frequency filter F forthe transmission of low frequency signaling current over thetransmission line simultaneous with the transmission of the variousbands of high frequency oscillations.

.FigureQ shows another variation of the general type of circuit whichdiffers from the circuit arrangement shown in Figure 1, in. that the lowfrequency and the high frequency transformers are connectet mutually inseries instead of in parallel as shown in Figure 1. These twotransformers may be replaced by one transformer suitably designed toefficiently transmit both high and low frequencies. The coils designatedand (4 represent the low frequency transformer and. the coils designated7) and 6 represent the high. frequency transformer. i'irnotherdistinguishing characteristic consists in the use of a single balancingnetwork N adapted to balance the high frequency line which may beconnected with a phtuality of terminal circuits.

in the figure, L represents a low fre quency line, having insertedtherein a low frequency band filter F and connected 'with two of thewindings of the triple winding transformer T L represents a highfrequency branch circuit having inserted therein a high frequency bandfilter F and connected with the opposite ends of the same two windingsof the transformer T with which the line L is also connected. Themidpoints of the said two windings of transformer T are connected withthe coil l of tar input transformer T the other coil of which isconnected across the input side of the duplex. translating circuit. Theoutput side of the said circuit is connected by nicai'is' of thetransformer T with the third winding of the said transformer T Bridgedacross the circuit L between the tiller F and the point of connection ofthe said circuit with the transformer T is a balancing circuitcontaining low freque11cy fil.- tcr F and network N which is adapted tobalance the low frequency line L Bridged across the circuit L, betweenthe filter F and the point of connection with the wind ings of thetransformer T is a balancing circuit containing high frequency filter Eand the network N, which is adapted to balance the main transmissionline h'lL with respect to a plurality of terminal networks.

In the operation ofthis circuit low fre quency currents are receivedover the line L, and will. pass through the filter F and be impressedupon the coil 1 of transformer T The high frequency oscillations fromthe source 3 will be modulated in accordance with the low frequencysignaling currents by the duplex translating circuit. The

modulated high frequency oscillations will be impressed by means oftransformer T upon the third winding of the transformer T and will setup similar oscillations in the circuit containing the other twowindings, which will pass tl'irough the high frequency filter F over thehigh frequency circuit L to the main transmission line ML. These highfrequency oscillations cantranslating circuit,

not pass into the low frequency line L since the filter F, is adapted totransmit only low frequency currents. in a similar manner the receivedhigh frequency oscillations arriving over the line L, will pass throughthe higl'i frequency band filter ll, (assining that they are within thathand of ireniencies which this filter is adapted to pass) and will beimpressed across the coil 2 of transformer T These high frequencyoscillations will combine with the unmodulated carrier oscillations fromthe source and will be demodulated in the The low frequency currentsderived thereby will be transmitted by the transformer T to the thirdwinding of the transformer T and will be impressed upon the receivingcircuit connected with the other two windings'of the transformer. Theselow frequency currents will pass through the filter F, into the lowfrequency line L, and actuate the low frequency naling apparatusassociated therewith. "llhese low frequency oscillations will not passback into the high freqiileucy circuit L since the filter F which isinterposed between the two circuits, is not adapted to pass lowfrequency currents. It will be seen therefore that this circuitarrangement provides means whereby the modulation of the transmittedwaves and the demodiiilation of the received waves may be performed by asingle translating circuit, which is connected with a single two-wirecircuit by means of a single triple winding transformer. Furthermore,this circuit arrangement shows a method whereby a single net work may beutilized with a plurality of terminal circuits to balance the main transmission line with which the plurality of terminal circuits may beconnected.

Since the circuit is balanced with respect to the conjugate transformerby means of the networks which are designed to approximate electricallythe line circuits connected with the end of the transformer oppositethat to which the network is connected, the translating circuit may beoperated so as to give greater amplification than the loss within thecircuit itself without producing singing around the circuit.

Although this invention has been disclosed as being embodied in aparticular form and arrangements of parts it is to he understood that itis capable of embodiment in other and different forms without departingfrom the spirit and scope of the appended claims,

l Vhat is claimed is:

l. in a signaling system, the combination with a high frequencytransmission circuit, of a low frequency signaling circuit, and atranslating circuit" interlinking said transmission and said signalingcircuits and having means common to the transmitting and receiving pathsof the oppositely traveling currents from said transmission circuit andsaid signaling circuit to modulate the curren from the said. signalingcircuit and to demodulate the currents from the said transmissioncircuit and means to impress the modulated and demodulated currents uponthe transmission and the signaling circuits respectively.

2. In a signaling system, the combination with a high frequencytransmission line having a high frequency band filter and a balancingnetwork connected therewith, of a low frequency circuit having a lowpass filter and a balancing network, a translating circuit common to thesaid high frequcl'icy line and low frequency circuit, and means toimpress currents from the said high fre quency line and the said lowfrequency circuit upon the said translating circuit, the saidtranslating circuit having means to modulate and demodulate theimpressed min-rents 3. In a signaling system, the combination with ahigh frequency circuit having high frequency band filters and abalancing net work associated therewith, of a low frequency circuithaving low pass filters and a balancing network associated therewith, atranslating circuit common to both. the high frequency and the lowfrequency circuit, a transformer coni'iecting the said high frequincyand the low frequency circuit with the input and the output sides of thesaid translating circuit, the said translating circuit having means tomodulate and de modulate themurrents from the said low frequency and thesaid high frequency circuits respectively.

in a signaling system, the combination with a h gh frequency circuit ofa low frequency circuit, a translating circuit having a frequencychanging device connected therewith, a conjugate transformer couplingthe said high frequency and the said low frequency circuits to the saidtranslating circuit, and a high frequenc band filter and a low passfilter insertedin the said high frequen j and the said low frequencycircuits respectively between the said circuits and the saidtransformer.

5. In. a signaling system, the combination with a high frequency circuitof a low frequency circuit, a translating circuit, a conjugatetransformer connecting the said high frequency and the said lowfrequency circuits to the said translating circuit, the said transformerhaving a plurality of windings each containing a high frequency and alow frequency coil in series for the transformation of high frequencyand low frequency currents,

6. in a high frequency signaling system, the combination of a source oflow frequency signaling current, a source of high &

frequency current, translating circuit having means common to thetransmitting and receiving paths of the oppositely traveling currentsfrom the said sources to modify both the transmitted and receivedcurrents, means for impressing the said currents upon the saidtranslating rircuit and frequency selecting means associated with thesaid source of signaling current and the said source of high frequencycurrent whereby interference between the respective sources isprevented.

7. In a high frequency signaling system, the combination of a lowfrequency signaling circuit, a high frequency transmission circuit, atranslating circuit having common means to modulate and demodulate thetransmitted 'and received currents respectively, high frequency and lowfrequency transforming means connected mutually in series for impressingsaid currents upon said translating circuit, and frequency selectingmeans associated with the said signaling circuit and said high frequencycircuit whereby interference. between the respective circuits isprevented.

8. A duplex system comprising a low frequency line, a high frequencycircuit, a modulator-detector circuit adapted to modulate currentspassing in one direction between said lineand said circuit and to detectcurrents passing in the other direction there between, a transformercoupling the said low frequency line and the said high fie quencycircuit to the said modulator-detector circuit, a network for balancingthe low frequency line and a filter for reducing the passage of highfrequency currents to the said network.

9. A duplex system comprising a low frequency line, a high frequencycircuit, a modulator-detector circuit adapted to modulate currentspassing in one direction between said line and said circuit and todetect currents passing in the other direction there between, atransformer coupling the said low frequency line and the said highfrequency circuit to the said modulator-detector circuit, a network forbalancing the high frequency line and a filter for reducing the passageof low frequency currents to the said network.

10. In a carrier current system, a hybrid the said line, a hybrid coiland a second high pass filter.

13. In a carrier current system, a high frequency line, a low frequencyline, means connecting said lines comprising a low pass filter adjacentsaid low frequency line, a high pass filter adjacent said high frequencyline, a hybrid coil between said filters, a

branch circuit containing a high pass filter and a balancing network forsaid high frequency line connected between said low pass filter and saidhybrid coil, a second branch circuit containing a low pass filter and alow frequency balancing network connected between said first mentionedhigh pass filter and said hybrid coil and a detector having its inputcircuit coupled to said hybrid coil and its output circuit coupledthereto in conjugate relation with respect to the said first coupling.

14. In a carrier current system, a high frequency circuit, a lowfrequency circuit, a single repeating device connected to said circuitsto repeat low frequency currents from said low frequency circuit as highfrequency currents to said high frequency .circuit and to repeat highfrequency currents from said high frequency circuit as low frequencycurrents to said low frequency circuit and individual balancing meansconnected with the said high frequency and the said low frequencycircuits at the points of connection of said circuits with the saidrepeater for simulating the impedances of both the said circuits.

In testimony whereof, I have signed my name to this specification this15th day of April 1921. r

LLOYD ESPENSGHIED.

